JPH02155376A - Picture input device - Google Patents

Abstract

PURPOSE:To keep the gradation of a part with a comparatively low brightness in an excellent even when the aperture is adjusted to a proper brightness by discriminating automatically a signal component with a very high brightness in a picture signal obtained from an image sensor such as a solid-state image pickup element and applying clipping. CONSTITUTION:A peak of a video signal and a data of an integration value are detected by a peak detection circuit 6 and an integration circuit 7 based on a video signal outputted from a 1st signal processing circuit 4 and the result is outputted to a comparison circuit 8, in which the necessity of the clipping by a clip circuit 10 is discriminated based on the input data and the discriminated data is outputted to the clip circuit 10. The clip circuit 10 clips the output signal of the 1st signal processing circuit 4 based on the data obtained via a latch circuit 9 from the comparison circuit 8 or outputs the non-clipped result to a 2nd signal processing circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to an image input device using a solid-state image sensor such as a CCD image sensor.

[Prior art] Recently, human-powered imaging devices such as surveillance cameras have a CCD in the shell.
Solid-state imaging devices such as image sensors are used. In such image input devices, the brightness of the subject is reduced to an appropriate amount of light using a lens system aperture mechanism, and the received image is converted into an electrical signal by a solid-state image sensor, which is then processed by a signal processing circuit connected to the subsequent stage. The signal is processed as a video signal of a predetermined format.

(The following is a blank space) [Problem to be solved by the invention] However, in the conventional device as described above, for example, the second
As shown in the figure, when a part of the subject includes a very high-brightness part (in this example, a light), if the aperture mechanism of the lens system adjusts the brightness to an appropriate level, a relatively low-brightness second part The gradation of the human face shown in the figure will be lost. In other words, for a signal containing very high luminance components, such as the waveform showing the luminance level in Figure 2, if the aperture is set to a low luminance part, when output to a monitor such as an electronic viewfinder, due to beam scanning, It becomes very difficult to see around high-brightness areas. As a result, the aperture must be adjusted to the high-brightness area, resulting in poor gradation in the low-brightness area.

An object of the present invention is to eliminate the above-mentioned drawbacks and to maintain good gradation in relatively low-luminance areas even when a part of the subject includes extremely high-luminance areas. An object of the present invention is to provide an image input device.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an image sensor that images a subject, and a peak value and an integral value of an image signal obtained from the image sensor. The present invention is characterized by comprising a discriminating circuit for discriminating whether a blob is essential or unnecessary, and a clipping circuit for clipping No. 19 that includes an abnormally high luminance in an image signal according to the discriminating circuit.

[Function] With the above configuration, the present invention automatically discriminates and clips extremely high-intensity signal components in an image signal obtained from an image sensor such as a solid-state image sensor. Even if the aperture is adjusted to an appropriate brightness, the tonality of the relatively low brightness portion can be maintained well.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the entire circuit configuration of an embodiment of the present invention, and the portion surrounded by a broken line frame A is the circuit according to the present invention.

In FIG. 1, reference numeral 1 denotes a lens with an aperture for capturing an image of a subject on a solid-state image sensor 2. As shown in FIG. The solid-state image sensor 2 captures an image of the subject through the lens l and converts it into an electrical signal. 3 is a sample and hold circuit for processing the output signal of the solid-state image sensor 2 into a signal that can be processed by the first signal processing circuit 4;

The first signal processing circuit 4 modulates the output signal of the sample and hold circuit 3 into a signal that can be demodulated by the second signal processing circuit 5, and forms a luminance signal Y and the like. Second signal processing circuit 5
demodulates the signal output from the signal processing circuit 4, has a clamp function to form a video signal and a function to add a synchronization signal, and outputs the video signal to the outside.

Next, to explain the circuit within the broken line frame indicated by A, 6 is the first
This is a well-known peak detection circuit that detects the highest level of the output signal of the signal processing circuit 4, and is reset by a vertical synchronization signal. 7 is a well-known integration circuit that detects the level of the integrated value of the same output signal of the first signal processing circuit 4. 68 is a well-known integration circuit that detects the level of the integral value of the same output signal of the first signal processing circuit 4. 68 uses the human power information obtained from the peak detection circuit 6 and the integration circuit 7 to determine the key points of the clipping operation, and This is a comparison circuit that determines whether it is unnecessary and outputs the determination information to the clip circuit IO. Reference numeral 9 denotes a latch circuit that latches the output of the comparator circuit 8 during the vertical retrace period m1. The clip circuit 10 clips the output signal of the first signal processing circuit 4 according to the determination information output from the latch circuit 9 and outputs it to the second signal processing circuit 5. 11 turns on and off the operation of this clip circuit lO.
This is a manual switch for F.

Next, the operation of the embodiment of the present invention will be explained. First, an image of an object formed on the solid-state image sensor 2 through the lens 1 is photoelectrically converted by the solid-state image sensor 2, and then inputted to the sample and hold circuit 3 as an electrical signal. This electrical signal is sampled and held by a sample and hold circuit 3 and outputted to a first signal processing circuit 4. In the first signal processing circuit 4, signal processing such as clamping and sw-y is performed on the human signal, and the processed signal is output to the clipping circuit IO.

At this time, based on the video signal output from the first signal processing circuit 4, the peak value and integral value data of the video signal are detected by the peak detection circuit 6 and the integration circuit 7, and output to the comparison circuit 8. . The comparator circuit 8 determines whether the clipping operation of the clipping circuit 1O is necessary or unnecessary based on these manual data, as described later, and uses the determined data as the clipping circuit 10.
Output to.

The clipping circuit JO clips the output signal of the first signal processing circuit 4 as described later using the data obtained from the comparator circuit 8 via the clipping circuit 9 as described above, or converts it to a second signal without clipping. It is output to the processing circuit 5. The clipping operation of this clipping circuit 10 can be selectively switched between ON and OFF by means of a switch 11. Further, the signal output from the clip circuit lo is demodulated by the second fε signal processing circuit 5 by clamping, adding a synchronizing signal, etc., and is output as a video signal. Although the present embodiment has been described with respect to a black and white monochrome camera, it is obvious that the same method can be applied to a color camera as well.

Next, a detailed explanation of the above-mentioned comparison circuit 8 and clipping circuit 1° will be provided.

FIG. 3 shows an example of the circuit configuration of the comparator circuit 8 shown in FIG. Third
In the figure, 12 is an input terminal for inputting the output signal of the peak detection circuit 6, and 13 is an input terminal for inputting the output signal of the integration circuit 7. 14 is a resistor for current limiting.

Reference numeral 15 denotes a Zener diode that boosts the potential of the integral value of the video signal input from the input terminal 13 in order to set it as a reference potential for comparison, and is connected in series with the resistor 14.

16 is a comparator that outputs a signal of 1li (high level) when the potential of the human input signal at the input terminal 12 is higher than the reference potential, and 17 is an output terminal of the output of the comparator 16.

To explain the operation of the comparator circuit 8 in FIG.
The video signal manually input from the input terminal 13 has a very high degree of precision, and for this signal, the potential obtained by boosting the integral value signal manually input from the input terminal 13 by the Zener diode 15 is used as a reference for the clip level of the portion to be clipped. Comparator 1G outputs a control signal for determining whether or not to perform clipping.
Output from.

FIG. 4 shows an example of the circuit configuration of the clip circuit 1o shown in FIG. In FIG. 4, 18 is an input terminal for manually inputting the output signal of the first signal processing circuit 4, and 19 is the output terminal (X
26 is an output terminal of the clip circuit 10. 2o and 25 are resistors for coupling. 21 and 24 are transistors for performing clipping ON and OFF operations, respectively, and 22 and 23 are resistors for setting the clipping level of the video signal, respectively.

To explain the operation of the clip circuit 1o in FIG. 4, the output signal of the latch circuit 9 inputted to the input terminal 19 is t, OW(
In the case of low level), the transistor 21 whose base is connected to the input terminal 19 through the resistor 20 is turned on (conducted), and the potential of the transistor 28 (collector potential) becomes the same as the power source 27 of the emitter. Therefore, the transistor 24 is turned off (
(non-conducting) and do not clip.

On the other hand, when the output of the latch circuit 9 is h+i (high level), the transistor 21 is OFF L, and the potential of the transistor 2B becomes the potential obtained by dividing the voltage of the power supply 27 by the resistors 22 and 23. Therefore, when the input terminal signal of the input terminal 18 has a constant vIlI: higher potential than the potential of the input terminal 28, the transistor 24 performs ONL/clipping that cuts only the abnormally high brightness portion.

The above operating characteristics are illustrated in terms of the relationship between the level of the output signal at the output terminal 26 and the level of the human input signal at the input terminal 18, as shown in FIG.

Therefore, according to the embodiment of the present invention, as shown by the hill and the line 'l in FIG. circuit lO
Since the aperture is clipped at , it is possible to set the aperture to match the low-brightness area, and avoid losing the gradation of the low-brightness area.

[Effects of the Invention] As explained above, according to the present invention, very high brightness signal components in image signals obtained from an image sensor such as a solid-state image sensor are automatically determined and clipped. As a result, even if the aperture is adjusted to an appropriate brightness, it is possible to maintain good gradation in relatively low brightness areas.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall circuit configuration of the embodiment of the present invention, FIG. 2 is an explanatory diagram showing an example of the waveform of an output signal for a subject in the conventional example, and FIG. 3 is the circuit configuration of the comparison circuit shown in FIG. 1. 4 is a circuit diagram showing an example of the circuit configuration of the clipping circuit shown in FIG. 1, FIG. 5 is a characteristic diagram showing the characteristics of the clipping operation of the embodiment of the present invention, and FIG. 6 is the embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of the waveform of an output signal for a subject. 4.5...A No. 8 processing circuit, 6...Peak detection circuit, 7...Integrator circuit, 8...Comparison circuit, 9...Latch circuit, lO...Clip circuit, 15. ... Zener diode, 16... Comparator, 21.24... Transistor. 1...Lens, 2...Solid-state image sensor, 3...Sample and hold circuit, Fig. 5 Fig. 4

Claims (1)

[Claims] 1) An image sensor that images a subject; a discrimination circuit that discriminates whether clipping is necessary or unnecessary based on the peak value and integral value of an image signal obtained from the image sensor; and the discrimination circuit. An image input device comprising: a clipping circuit that clips a signal including abnormally high brightness among the image signals according to the determination.